Control apparatus



Sept. 8, 1942.

M. w. EATON CONTROL APPARATUS Filed Aug. 5, 1940 2 Sheets-Sheet l M. W. EATON Sept. 8, 1942.

CONTROL APPARATUS Filed Aug. 3, 1940 2 Sheets-Sheet 2 0 f 7 .5 2 I I ET. o u i i Z 2 r I 6 4 3 Mu/ t-Frr I a 4 I A 7 M J 6 A, a

q n 3% u/ I L L .F l r l I M4 wu/ M5970 Patented 8, 1942 UNITED STATES PATENT OFFICE t 3,295.4 t I Malcolm wm rzifli m to Micro Switch Corporation, Irecport, Ill, a oornotation of Illinois Application Aligllst 3, 194., N0. 350,732

6Claiml.

The present invention relates generally to electric switches and thermostats.

Objects of the invention include the provision of an improved electric switchthat may be actuated thermostatically. and that also may be actuated manually or by other external means.

Its objects include also the provision of an improved construction and actuating mechanism for an electric switch. These and other obiects 1 and advantages of the invention will become apparent as the description proceeds. The invention resides in certain novel features of construction, combination of parts, and arrangements of apparatus. particularly set forth in the claims, and is illustrated by the specific embodiments herein shown and described by way of example. In the drawings:

Fig. l is an elevational view, partly in section illustrating one embodiment of the invention;

Figs. 2-and 3 are partially exploded views-of the device of Fig. 1 illustrating in perspective, the various'parts and their orientations with respect to each other in the assembly;

Fig, 4 is an elevational view of another embodimentof the invention; and

Figs. 5 and 6 are partially exploded views of the device of Fig. 4 illustrating in perspective, its various parts and their orientations in the assembly. I

In the device of Figs. 1, 2, and 3 a moulded insulating base I2 includes a bed portion l4 onwhich it carries a spring-supporting anchor ll formed of brass. This anchor i6 is generally U- shaped, as seen in Fig. 3, and has half-punches it at the ends of its legs 20 to set down into cating holes 22 in the insulating base. This anchor I0 is held by a molded insulating block 24, which clamps the two ends of the legs of the anchor It to hold it in place on the molded plate. Anchor It being held only at one of its ends, may be flexed to raise and lower the other end. Screw 2B threaded up through the base l2, as shown in Figs. 1 and 3, turns up against theright hand end of the anchor it (as seen in the drawings) to raise it slightly oil the insulating base for adlusting the operation of the device in a manner to be described presently. Lying. under the right hand end of the anchor It is a lever 28. This lever 24 lies in a recess in the bed portion i4 of the base and is in part held in place by the sides of the recess. An upturned end 44 of the lever 2! lies between the end of the anchor II and the end of the recess of the base to further hold the lever 28 in place. The left end of the extends up through the insulating base (best seen mm. 1) so that this push buttonmaybepushed' ,up to raise the lever 28 to in turn liftthe right end of the anchor'oi! the adjusting screw 24, the lever 24 iulcruming at its right end and, engaging the anchor It at the throat 44.

The right hand end of the anchor it carries two upturned tabs 38; which are notched to receive threads of a pair of bowed thin-leaf compression springs 34. The ends of these compression springs 38, as shown in Fig. 3, are flat in their unstressed condition, and constitute different portions of a single U-shaped spring. At. the closed end 40 of this spring is riveted one end. of a bimetal strip 42, the other end of which is supported on an insulating projection 44 of the base II. A .terminal member 46 and insulating guard 48 (see Figs. 1 and 2) lie over this right hand, mounted, end of the bimetal strip 42 and are clamped in place thereon by a screw 50 which threads into a metal insert 52 (Fig. 1) embedded in the insulating material of the base. The bimetal strip 42 constitutes a tension member or thin tension spring. The thin compression springs 38, together with the bimetal strip 42, constitute a snap acting toggle 54 which carries a contact 56 at its movable end 40. Since the radius oi action. of the compression springs 38 is less than that of the tension bimetal strip 42, the toggle 54 has an over center snap characteristic. An insulating push button 58 extending up through the base is adapted to press up against the bimetal strip close to its mounted end, that is between the mounting of the compression springs 38 and the mounting of the tension member 42, for inducing a snap action of the spring toggle 54. i t

A terminal member 60 lies atop a raised portion 62 at the left end of the insulating base (Fig. 2) and is spaced thereby slightly above the legs 20 of the anchor It. The insulating block 24 has its under surface stepped to fltover the two anchor legs 20 and over the terminal 60 for clamping all of them securely in place. Another terminal member 84 lies in a recess on the top of block 24 and over this is laid the insulating guard lever 2. lies over the top of a push button 82 that 48 secured'by a screw threaded into a metal insert 88 embedded in the molded base (Figs. 1 and 2). The terminal plates and 64 constitute stops for limiting the snap motion of the toggle 64 and they carry stationary buttons 68 and I0 respectivelyfor cooperating'with the lower and upper surfaces of the contact 56 carried by the toggle 54.

The bimetal element 42 in this particular embodiment is constructed with its high expansion material on the upper face so that on a rise of temperature the bimetal tends to move the contact 55 down, and similarly on a fall of temperature, tends to move contact 55 up. Thus when the toggle 54 lies in its uppermost position, as shown in Fig. 1, the bimetal element 42, upon a rise of temperature tends to arch into a position concave downward so as to move the contact 55 down. However, this action of the bimetal is opposed by the toggle characteristic of the spring structure so that the bimetal 42 causes no downward motion of the contact until it overcomes the spring force of the toggle and thereupon moves the contact with a snap action down against the lower stationary contact 53. The force of the springs 38 and therefore, the toggle characteristic of the action, is sufllciently great compared with the rigidity of the beam action of the bimetal strip 42 that the moving contact 55 is held firmly engaged with the upper stationary contact 10 until, at a certain temperature, the snap action takes place. Similarly, upon the fall of temperature the contact 55 is snapped from its lowermost to its uppermost position.

' The number of degrees diiference between the two temperatures at which the bimetal element snaps the contact up and down is determined by the spacing between its two stops, that is between the two stationary contacts 68 and 18, compared to the dimensions of the spring 38 and the bimetal element 42 themselves. An adjustment of the screw 25 to alter the position of the mounting points of the two springs 38, raises or lowers the two operating temperatures together without substantially changing the difference between those two temperatures.

The toggle 54 may also be operated by actuation of the push buttons 32 and 58. When the toggle 54 is in its uppermost position as shown in Fig. 1, it may be snapped to its lowermost position by pushing up the button 32 to raise the anchor l5. This raising of the anchor l5 brings the mounting points of the two compression springs 38 above the tension line of the bimetal strip 42 for reversing the direction the spring toggle tends to move the contact 56. Upon release of the push button 32 the toggle will either remain in its lowermost position, or immediately return to its uppermost position, depending upon the temperature of the bimetal element 42. When the spring toggle is lying in its lowermost position, it may be snapped to its uppermost position by an upward actuation of the push button 58. The push button 58 bearing upward against the bimetal element 42 bends it upward so as to carry its tension line up above the pivot axis of the support for the two compression springs 38 so that the toggle immediately snaps the contact 55 to its uppermost position. Upon release of the pressure on the button 58, the toggle either remains in its upper position or returns to the lower position, depending on the temperature of the bimetal element 42.

The push buttons 32 and 58 slide in counterbores 12 and 14 respectively, which limit their upward motion. If the bimetal element 42 is at a sufficiently low temperature, push button 32 will lowering of this snap-down-temperature-setting of the toggle 54. The bimetal element 42 must be at, or above, that so-called minimum setting. Similarly, the limit on the upward motion 01' push button 58 requires that bimetal element 42 be at or below a certain temperature, in order that the push button 58 be effective for snapping the toggle 54 to its upper position. Preferably the counterbores 12 and 14 are made deep enough to let both of the push buttons 32 and 55 be eflective at some one temperature range of the bimetal strip 42. Above this temperature range, only push button 33 i effective, and below it, only push button 58 is effective, for manual actuation of the switch. On the other hand, it the two push buttons 32 and 53 have their upward motions considerably limited, there will be a temperature range in which neither push button is effective for operating the switch.

In the embodiment of Figs. 4 to 6 inclusive, a spring supporting anchor I3 is clamped in place by the insulating block 24 as in Figs. 1 to 3. A tab 21, riveted to the right hand end of the anchor I5, extends between and beyond the upturned tabs 35 and over a push button 33, which is arranged to lift the anchor of! the adjusting screw 25 for operating the switch. The spring toggle 54 with its bimetal element 42 is supported as in Figs. 1 to 3 and carries a single faced contact 51 at its movable end. The terminal member 54 carrying the stationary contact 18 serves as the upper stop for the toggle. The toggle 54 in its lowermost position stops against the overlying retaining Spl'ing 55 of a manual push button 59. Push button 33 has its upward motion limited by counterbore 15 in which it slides. Accordingly, the bimetal strip 42 must be at or below a certain temperature (determined by the movement allowed the button 33) if push button 33 is to be effective for snapping the toggle to the open circuit position.

Push button 59 lies in the counterbore I8 and has its upper motion limited thereby so that the push button 59 cannot move up against the toggle 54 when the toggle 54 lies in its uppermost posi tion. Accordingly, push button 58 is incapable of moving the toggle 54 upwards far enough to force the contacts 51 and 10 into engagement.

As in the device of Figs. 1 to 3, whether or not either one or both of the push buttons 33 and 53 are effective for operating the switch at some particular temperature of bimetal strip 42 depends on the motion allowed those buttons in their respective counterbores. For example, when this device of Figs. 4 to 6 is employed for controlling an electric motor or the like, the screw 25 is so adjusted that bimetal 42 opens the circuit at the maximum safe temperature of the motor and push button 59 has its upward motion limited to require that the motor, and also bimetal 42, cool considerably before push button 58 can reclose the circuit. But push button 33 is permitted sufllcient motion that it will be effective for opening the circuit at all temperatures to be encountered when the motor is in use.

The toggle 54 is adapted to be snapped up and down by its bimetal element 42 in response to changes in temperature for closing and opening the circuit between the two contacts 51 and 18. The temperature difference between the turn on and turn all points is determined in part by the distance through which the toggle moves and so is greater when the push button 58 lies in its lowermost position than when push button 59 is held in its uppermost position. As before, the adjusting 'out returning the contact to its uppermost position. However, if it cools sufilciently, push button 59 may be moved to its uppermost position and toggle 54 will thereupon snap away from .push

button 59 into its uppermost position where it holds contact 51 against stationary contact 10.

The screw 26'may be adjusted to such a position that the temperature to which the bimetal element 42 must cool before snapping the toggle up out of its lowermost position (when the push button 59 lies in its lowermost position), is lower than any temperature that might be encountered in practice. With such an adjustment the switch will return to its closed position only when the bimetal element cools sufllciently and at the same time push button 59 is held in its uppermost position,-

In both embodiments, the bimetal element 42 may conduct current and be heated thereby for the operation of the switch. Thus in an electric motor or the like, the thermal element 42 may conduct the energizing current of the motor and so be heated thereby, and it may also be exposed -to the heat of the motor itself, as for example, by being mounted inside of the motor housing.

It will be readily apparent that I have provided a novel and improved thermostat construction which is capable of numerous variations and modifications within the scope of the appended claims.

I claim:

1. In combination, a sprin snap mechanism including a thermostatic bimetal strip for actuating said snap mechanism back and forth, stops for limiting the snap motion of said mechanism, whereby said mechanism snaps back and forth between said stops in response to rise and fall of the temperature of said bimetal element between predetermined values of temperature, a I

first manually actuable means for operating said mechanism to snap it in one of the two directions between its stops, and second manually actuable means for snapping said mechanism in the other direction between its stops.

2. The combination of the immediately preceding claim wherein there is included a stop for limiting the motion for said second manually actuable means whereby said second manually actuable means is capable of inducing said snap motion in said other direction, only if said bimetal element has a temperature within a predetermined range.

3. In combination, a snap acting thermostatic switch including contacts operated thereby, and

including also a bimetal element responsive to a rise in temperature for opening said contacts with a snap action, a manually actuable means for forcing said contacts toward closed position against the tendency of said snap acting mechanism to hold said contacts open, means for limiting the motion of said manually actuable means short of the closed position of said contacts, whereby said manually actuable means is incapable, by itself, of closin said contacts, and second manually actuable means for operating said snap mechanism to cause said snap mechanism to open said contacts with a snap action.

4. In combination in a snap acting thermostatic electric switch, a bimetal element for operating said contacts back and forth with a snap action in response to a change of temperature though a predetermined temperature difierential, manually operable means for acting on said mechanism for urging it to snap in one direction by moving one of the two limiting temperatures (between which said bimetal element must change its temperature for actuating said switch back and forth) toward the other of said two limiting temperatures, means for limiting the motion of said manually actuable means to prevent it from reducing said temperature differential to zero, and manually actuable means for urging said snap mechanism to operate in the opposite direction.

5. A combined thermal protector and manual on-off switch for an electric motor, or the like, comprising contacts, a snap acting thermostatic mechanism including a bimetal element responsive to a rise in temperature for snapping said mechanism to open said contacts, a first manually actuable means for operating said mechanism to snap said contact open regardless oi the temperature of said bimetal element, second manually actuable means for operating on said mechanism to cause it to snap said contacts closed, and a stop for limiting the motion of said second manually actuable means.

6. In combination, a spring toggle snap mechanism comprising a flexible thin-leaf tension member and a compression member, means acting on said thin-leaf tension member to hex it laterally for inducing a snap operation of said snap mechanism, second means acting on the support for said compression member to move said support laterally for inducing a snap operation of said snap mechanism, and a stop for limiting the motion of one. of said means, whereby to limit the force it can exert on said snap mechanism, said snap mechanism including thermostatic means for actuating itself in response to a change of temperature.

MALCOLM W. EATON. 

